Lubricating oil compositions comprising mercaptobenzothiazole ester derivatives



LUBRICATING OIL COMPOSITIONS COMPRISING MERgAPTOBENZOTI-IIAZOLE ESTER DERIVA- Arnold J. Morway, Clark, and Jelfrey H. Bartlett, New

Providence, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Original application Sept. 28, 1955, Ser. No. 537,304. Divided and this application Feb. 21, 1958, Ser. No. 716,531

6 Claims. (Cl. 252-475) This invention relates to mercaptobenzothiazole carbox-ylic acid and ester derivatives thereof and compositions containing the same. More particularly, the invention relates to mercaptobenzothiazole low molecular weight carboxylic acid and high molecular weight ester derivatives. The compositions of the invention include lubricating oils, lubricating greases, gear oils, hydraulic fluids, cutting oils, etc.

This application is a division of our copending application Serial No. 537,304, filed September 28, 1955, and

-. now abandoned.

Mercaptobenzothiazole is a well known vulcanizing accelerator useful in the preparation of rubber. Compounds of this type which contain a high percentage of sulfur in a non-corrosive form, would be a very desirable lubricant constituent, since it has been previously established that sulfur-containing compounds will enhance the load-carrying or extreme pressure characteristics of lubricants. Mercaptobenzothiazole is, however, substantially insoluble in mineral or synthetic lubricating oils. In accordance with the invention, it has now been found that certain mercaptobenzothiazole carboxylic acid and ester derivatives are soluble in oil, and that these sulfurand. nitrogen-containing compounds can be eifectively utilized as lubricating oil and grease constituents. More particularly, it has been found that certain Z-mercaptobenzothiazole acetic or propionic esters may be advantageously employed as extreme pressure additives in lubricating oil compositions. Furthermore, these ester compounds may be employed as the grease base or soap dispersant of lubricating grease compositions. In accordancewith another aspect of this invention, it has been found that the acetic or propionic acid derivatives of 2-mercaptobenzothiazole can be employed as a constituent of a grease thickener, especially a metal soap-salt complex thickener.

The mercaptobenzothiazole compounds contemplated in this invention are represented by thevfollowinggeneral structural formula wherein n is an integer equal to l and 2, and R is selected from the group consisting of hydrogen and an aliphatic alkyl radical having from 8 to 20 carbon atoms. The alkyl group can be either straight or branched chain. Examples of the acid derivatives include:

Z-mercaptobenzothiazole acetic acid 2 -mecaptobenzothiazole propionic acid The ester derivatives are exemplified by:

2-mercaptobenzothiazole acetic acid lSOfOClZYI; ester Z-mercaptobenzothiazole acetic acid C Oxo ester, Z-mercaptobenzothiazole acetic acid non-yl ester; Z-mercaptobenzothiazole acetic acid dodecyl ester.

" Nonyl alcohol Patented May. 23,1961.

2-mercaptobenzothiazole acetic acid tridecyl ester Z-mercaptobenzothiazole acetic acid i'sotridecyl ester Z-mercaptobenzothiazole acetic acid C Oxo ester Z-mercaptobenzothiazole acetic acid tetradecyl ester Z-mercaptobenzothiazole acetic acid hexadecyl ester Z-mercaptobenzothiazole acetic acid octadecyl ester 2-mercaptobenzothiazole acetic acid arachidyl ester CSH+NaOH or NaO CH:

C'SNa-l-HzO or CHsOH wherein X is a halogen selected from the group consisting of chlorine, bromine and iodine, and n is an integer equal to 1 and 2. Examples of the monohalogenatedcarboxylic acids include: monochloroacetic acid, monobromoacetic acid, monoiodoacetic acid, monochloropropionic acid', monobromopropionic acid, and monoiodopropionic acid. Potassium hydroxides may be used in, place of sodiumhydroxide or sodium alkoxide in the preparation of the alkali metal salt of mercaptobenzothiazole.

Temperatures Within the range of about 0 to 50 C. are employed in preparing the alkali metal salt of mer captobenzothiazole. The alkali metal salt of mercaptobenzothiazole is then reactedwith the alkali'metal' salt of monohalogenated acetic or propionic acid, for example, at temperatures in the range of about 0 to C.

The preparation of ester derivatives of mercaptobenzothiazole acetic and propionic acids can be readily ac+ complished by reacting the alkali metalsalt of mercapto; benzothiazole with esters of the monohalogenated sub stituted acetic and propionic acids at temperatures within the range of about 0 to 75 C. The esters of the monohalogenated substituted acetic and propionic acids corre spond to the following general formula:

where X. is a halogen selected from the group consisting of chlorine, bromine and iodine, n is an integer from 1 to 2, and R is a straight or branched chain aliphatic alkyl radical containing from 8 to 20 carbon atoms, which is derived fromthe.correspondingalcohol: The above esters are prepared by esterifyingtlie correspond ing monohalogenated' substituted; carboxylic acids? with an alcohol having-the desired number; of carbon atoms. Alcohols contemplatedin- ,this invention included;

Oct-yl alcohol Iso-octyl alcohol Cg ,Oxoalcohol 'I'sod'odecyl alcohol Tridecyl alcohol Isotridecyl, alcohol Ci 0x0 alcohol] Decyl alcohol Tetradecyl alcohol Isodecyl alcohol Hexadecyl alcohol Dodecyl alcohol Octadecyl alcohol, etc.

It will be noted that branched chain as well as straight chain aliphatic alcohols may be employed in preparing the ester derivatives of mecaptobenzothiazole. The Oxo alcohols described above are prepared by catalytically hydrogenating the aldehydes prepared in the well known Oxo process, which involves the carbonylation of olefins with carbon monoxide and hydrogen in the presence of a cobalt catalyst at a temperature of about 300 to 400 F. and a pressure of about 2500 to 4000 p.s.i.g. The mono-olefinic carbonylation feed can comprise to C olefins derived from cracked gases, from Fischer-Tropsch products or from polymers of ethylene or propylene. The 0x0 process as well as the preparation of 0x0 alcohols are described in detail in US. Patent No. 2,5 93,- 428, issued April 27, 1952, to Fischer, Knoth and Newberg. The 0x0 alcohols contemplated in this invention are branched chain saturated aliphatic alcohols.

The ester derivatives may also be prepared by esterifying the Z-mercaptobenzothiazole acetic or propionic acid, prepared as described above, directly with one of the alcohols, listed above. This method is illustrated as follows:

wherein n is an integer equal to 1 or 2 and R is a straight or branched chain aliphatic radical containing from 8 to 2.0 carbon atoms.

In the following example the preferred method of preparing the ester derivatives of Z-mercaptobenzothiazole is described.

EXAMPLE I A. Preparation of mercaptobenzothiazole acetic acid A 3 liter 3 necked flask equipped with a stirrer and thermometer was charged with 285 g. of chloroacetic acid and 700 cc. methanol. This mixture was cooled to 0 C. and then treated with 163 g. of sodium methoxide dissolved in 500 cc. methanol, thus yielding the sodium chloroacetate.

A 5 liter 4 necked flask was also set up and was equipped with a stirrer, condenser, thermometer and dropping funnel. It was then charged with 501 g. (3 m.) mercaptobenzothiazole and 800 cc. methanol. To this mixture was added 162 g. sodium methoxide dissolved in 500 cc. methanol. The resulting mixture was cooled to 0 C. and then the sodium chloroacetate solution was added through the dropping funnel over a period of about minutes. Heat was applied and gradually raised to 68 C. during 1 /2 hours. Then the product was transferred to a 12 liter flask where it was dispersed in water and acidified with HCl followed by 3 water washes. The washed product was dissolved in a mixture of benzol and methyl ethyl ketone, dried with Na SO filtered and evaporated on a steam bath leaving a solid residue of 562 g. of 2-mercaptobenzothiazole acetic acid. Acid No.=0.403 ceq./ gm.

B. Preparation of the C 0x0 ester of mercaptoben zqthiazole acetic acid A 2 liter 3 necked flask equipped with a stirrer, thermometer and a water trap with a condenser was charged with: Mercaptobenzothiazole acetic acid g 113 C 0x0 alcohol g 200 l Toluene sulfonic acid g 1 Toluene cc 400 The above mixture was refluxed for 3 /2 hours at -125 C. during which time 15 cc. of water was collected in the trap. The resulting product was diluted with 500 cc. toluene and given 3 washes with 5% NaOH followed by 3 water washes, then evaporated on the steam bath for removal of the toluene.

The residue was stripped in a short path still to a pot temperature of 210 C. at 0.5 mm. leaving 175 g. of hottoms. This was treated with 15 g. of Super Filtrol clay at C. for 5 minutes and filtered through l-Iyllo leaving a finished ester with the following analysis:

Acid No. 0.010 ceq./gm. Ester No.=0.266 ceq./ gm.

C. Preparation of isooctyl ester of mercaptobenzothiazole acetic acid A 3 liter 4 necked flask equipped with a stirrer, condenser, thermometer and dropping funnel was charged with 334 g. mercaptobenzothiazole and 600 cc. methanol. To this mixture was added 110 g. sodium methoxide dissolved in 500 cc. methanol. The resulting mixture was minutes. After cooling to 55 C. the mixture was filteredthrough Hyflo. The methanol was then evaporated, and the residue distilled in a short path still. A fraction ot 274 g. was obtained at to 185 C. at 0.7 mm. with most of it boiling at C. There was a remaining residue of 56 g.

As noted above, the Z-mercaptobenzothiazole aliphatic esters of the invention can be efiectively utilized as load carrying or extreme pressure additives in lubricating oils. Mineral lubricating oils are the preferred menstrua, and they may be any of the well known mineral lubricating oils with which the art is familiar. Petroleum distillates from either naphthenic or paratlinic base stocks having a viscosity from'about 35 to 250 SUS at 210 B. may be used as well as mixtures of the same; the choice of base oil depending upon the lubricating service contemplated. Synthetic lubricating oils may also be used as the vehicles such as hydrocarbon, hydrocarbon polymer, ester, complex ester, formal, mercaptal, polyalkylene oxide, silicone or similar types. More particularly, synthetic oils such as di-Z-ethylhexyl sebacate, di-C Oxo azelate, and other branched chain simple esters of dicarboxylic acids as well as complex esters prepared from glycols, dicarboxylic acids and alcohols and/or monocarboxylic acids. Mixtures of mineral and synthetic oils may also be employed. For special applications, .animal, vegetable or-fish oils, or their hydrogenated or voltolized products may be employed, either alone orin'admixture with mineral oils. The amount of the mercaptobenzothiazole carboxylic acid ester additive used in the lubricating oil will ordinarily be from about 3 to 15 wt. percent, preferably about 5 to 10 wt. percent, based on the total weight of the compositions.

EXAMPLE II 1 Dlatomaceous earth.

a 4 A .l.d.. mi

5 additive properties. The composition and properties of the lubricating oils tested are tabulated below:

TABLE I umen Test Composition Weights Pm Con- Oarried dition (A) Mineral lubricating oil (55 SUS 210 F.) 2 Sheared. (B) Mineral lubricating oil (55 SUS 210 F.)+ 15 Excellent.

5 Wt. percent'oi 2-mercaptobenzot-hiazole acetic acid 013 x0 ester;

(0) Mineral lubricating oil (55 SUS 210? RH: 15 Do.

10 wt. percent of 2-mercaptobenzothiazole acetic acid 0 3 0x0 ester.

(D) Mineral lubricating oil (55 SUS 210? l*.) 15 Do.

10 wt. percent of 2-mercaptobenzothiazole acetic aeidCa 0x0 ester.

It will be noted from the above data that the esters of the invention are valuable as lubricating oil additives for enhancing the load-carrying or extreme pressure characteristics.

' In accordance with another aspect of the invention, the Z-mercaptobenzothiazole carboxylic acid esters of the invention can also be employed as grease bases or as the dispersants for metal soap, met-a1 soap-salt complex or metal 'mixed salt complex grease thickeners. Non-soap grease thickeners such as silica gel, hydrocarbon polymers, etc., may also be used. When employed as the grease base the esters of the invention will ordinarily be used in amounts within the range of about 50 to 95 wt. percent, preferably about 60 to 90 wt. percent, based on the total weight of the grease composition. It is also conitem'plated that any of the conventional grease additives such as oxidation inhibitors, pour depressants, corrosion inhibitors and the like can be incorporated in the grease compositions described above.

The following example is illustrative of grease compositions prepared in accordance with this feature of the invention.

EXAMPLE III A lubricating grease was prepared from the following ingredients:

Formulation Percent Weight Glacial acetic acid 12. 0 Commercial capric acid 1 6.0 Hydrated lim 9. 8 Phen'yl 'alpha-naphthylamme 1. 0 2 mercaptobenzothiazole acetic acid 013 Oxoestern 71. 2

Percen 1 Caprylic acid 24.

Ca'pric' acid 57. Laurie acid 17. 8

jacket. The resulting grease composition was then Gaulin homogenized at 6000 p.s.i. Properties:

'Appearance Excellent, smooth,

uniform. Droppingpoint, -F 500+. Penetrations (77 F. mm./10)

Unworked 275. Worked (60 strokes) 295.

6 Norma-Hoffman oxidation test v I f (hrs. to 5 p.s.i. drop) 350. Lubrication life, hours (250 F., l

10,000 rpm.) 1700+. Extreme pressure properties,

Timken test lbs.) Pass. Shell four ball test (extreme pressure index) 50.3.

Other conventional grease thickeners, both soap and non-soap types, may be employed in place of the mixed metal salt complex described in Example III when the ester derivatives of Z-mercaptobenzothiazole of the inventionare'u'tilized as grease bases. For example, any of the commonly known grease-making soaps such as the metal soaps of high molecular weight saturated or unsaturated'carboxylic acids having from 12 to 30 carbon atoms 'per molecule, preferably about 16 to 22 carbon atoms, may be utilized. Operable metals include the alkali metals; sodium, lithium and potassium; and the alkaline earth metals: calcium, barium, strontium and magnesium. The high molecular weight fatty acids are exemplified by lauric acid, myristic acid, palmitic acid, stearic acid, liydroxy stearic acid, oleic acid, hydrogenated fish 'oil acids,'linoleic acid, arachidic acid, behenic acid, etc. Glycerides of the above acids, vegetable fat, tallow, etc. may also be employed as the saponifiable material.

' Suitablecomplex thickening agents include:

(a) The soap-salt complexes prepared from the metal salts of low molecular weight carboxylic acids having from 1 to 3: carbon atoms per molecule, and metal soaps of molecular weight carboxylic acids having from 12 to 30 carbon atoms per molecule, wherein the mol ratio of the low to high molecular weight acids is about 1:1 to 40:1, preferably about 8:1 to, 25:1.

(b) The mixed salt complexes, as described above in Example III, prepared from the metal salts of low molecular weight carboxylic acids having from 1 to 3 carbon atoms per molecule, and metal salts of intermediate molecular weight carboxylic acids having from 7 to 10 carbon atoms per molecule, wherein the mol ratio of low to intermediate molecular weight acids is about 2:1 to 40:1, preferably about 4:1.to 25 :1.

(c) The soap-salt complexes prepared from a metalsalt of acetic acid, metal salts of medium molecular weight carboxylic acidshaving from 3 to 10 carbon atoms per molecule and metal soaps of high molecular weight carboxylic acids having from 12 to 30 carbon atoms per molecule; wherein the mol ratio of acetic acid to the medium and high molecular weight acids is about 0.5 :1

' to 1011, and the difference in number of carbon atorns preparing the complex thickeners described above are the.

Well known saturated and unsaturated, grease-making fatty acids which were previously described with respect to the preparation of the conventional metal soap grease thickeners.

The. intermediate molecular weight acids are those aliphatic 'monocarb oxylic acids containing from about 7 to 10 carbon atoms, preferably about 8 or 9 carbon, atoms, per molecule. Either saturated or unsaturated fatty acids may be utilized, although the saturated fatty;

' acids are preferred. Suitable acids include: 5-methyl-2 hexanoic, heptano'ic, octanoic, Z-ethyl-hexanoic, C Oxo, nonanoic, decanoic, C 0x0 acids, etc.

The medium molecular weight carboxylic acids include straight and branched chain saturated aliphatic carboxylic. acids, hydr oxy aliphatic monoand poly-carboxylic acids, aromatic monoand poly-carboxylic acids and anhydrides thereof, and-heterocyclic acids containing from aboutfi' to 10, pr eferably about 6 t ;9',jcarbon atoms P moleru e. Suitable ac s; nc de: p n a hexanoic, heptanoic, octanoic, nonanoic, decanoic, isobutyric, C 0x0, C Oxo, C Oxo, C Oxo, glyceric, benzoic, hydroxy benzoic, toluic, o-phthalic, phthalic anhydride, terephthalic, furoic, thiophene carboxylic, etc.

The low molecular weight carboxylic acids capable of being used in the preparation of the complex thickeners include saturated and unsaturated carboxylic acids having from about 1 to 3 carbon atoms per molecule, such as formic, acetic, acrylic and similar acids including their hydroxy derivatives, e.g. lactic acid. Monocarboxylic acids are particularly useful, and acetic acid is especially preferred.

The alkaline earth metals such as calcium, barium and strontium are particularly useful for preparing the complex grease thickeners. Calcium is especially preferred. The alkali metals such as sodium, potassium and lithium can also be employed, though they are not as efiective' for the preparation of these complex thickeners as the alkaline earth metals. Magnesium and zinc can also be used for this purpose.

In general, the amount of metal soap or complex grease thickener in the Z-mercaptobenzothiazole carboxylic acid ester base greases of the invention will vary from about 2 to 20 wt. percent, preferably from about 4 to wt. percent; the percentages being based on the weight of the total composition.

In accordance with another feature of this invention,- the low molecular weight carboxylic acid derivatives of Z-mercaptobenzothiazole are useful in the preparation of the metal complex grease thickeners described above. The carboxylic acid derivatives contemplated in this aspect of the invention correspond to the following structural formula:

wherein n is an integer equal to 1 and 2. More particularly, it has now been found that Z-mercaptobenzothiazole acetic and propionic acids can be effectively utilized in the preparation of metal soap-salt complex grease thickeners.

EXAMPLE IV A lubricating grease composition was prepared from the following ingredients:

Formulation Percent Weight Glacial acetic acid z-Mercaptobenzothiazole acetic acid Stearic acid Hydrated limo Phenyl alpha naphthylamine Mineral lubricating oil (55 BUS 210 1* Moi ratio (acetic to higher acids) Moi ratio (2-mercaptobenzothiazole acetic acid to stearic acid)- q r psws s Preparation.-The mineral lubricating oil, the lime, stearic acid and Z-mercaptobenzothiazole acetic acid were charged to a fire heated grease kettle with stirring to 1 form' a slurry. The slurry was warmed to 140 F., the acetic acid added, and the heating continued to a temperature of about 500 F. The heating was then discontinued, and the grease mixture was cooled to 200 F. while agitating. At this point, phenyl alpha naphthylmine was added, and the grease mixture was Gaulin homogenized at 6000 p.s.i.

Penetration (77 F. min/10)- Unworked 300. Worked (60 strokes) 310. Worked (100,000 strokes) 355. Phase change up to 400 F. None. Norma-Hoffman oxidation test (hrs. to 5 p.s.i. drop) 350. Lubrication life, hours (10,000

r.p.m., 250 F.) 1034. E.P. properties, Almen shock load 15 wgts., excellent pin condition. Timken test (45 lbs.) Pass.

Discontinued test. Inspection of bearings and grease showed them to be in good condition.

The calcium soap-salt complex thickener of the above example is similar to the complex thickener type (0) described above, with the exception that Z-mercaptobenzothiazole acetic acid is employed as the medium molecular Weight carboxylic acid. The metals, the low molecular weight carboxylic acids and the high molecular weight carboxylic acids described above in connection with type (c) are also applicable for preparing the metal soap-salt complex thickeners of this invention.

Mineral or synthetic lubricating oils described above with respect to the lubricating oil composition of the invention can also be utilized as the grease base for this feature of the invention. percent, preferably about 5 to 30 wt. percent, of the complex grease thickener is employed with from about 60 to 98 wt. percent, preferably about 70 to wt. percent, of the oleaginous vehicle.

In brief summary, the invention pertains to 2-mercaptobenzothiazole acetic or propionic acids and ester derivatives thereof, corresponding to the following structural formula:

wherein n is an integer equal to 1 and 2, and R is selected from the group consisting of hydrogen and a straight or branched chain, aliphatic alkyl radical having from 8 to 20 carbon atoms. The ester derivatives of the invention can be utilized as lubricating oil additives in amounts of about 3 to 15 Wt. percent to contribute extreme pressure properties to the final lubricating oil composition. These ester derivatives may also be eflfectively utilized in amounts ranging from about 50 to wt. percent as grease bases or soap dispersants in the preparation of lubricating grease compositions having long lubrication lives and excellent extreme pressure characteristics as well as other desirable grease properties.

It is also Within the scope of the present invention to employ the acetic and propionic acid derivatives of 2- mercaptobenzothiazole themselves as constituents in the preparation of metal soap-salt complex grease thickeners.

The invention is not limited to the specific materials and conditions of the foregoing examples. These materials and conditions may be varied within the limits indicated in the general portions of the specification. Though the acetic and propionic acid and ester derivatives of 2- mercaptobenzothiazole are the preferred compounds of the invention, the invention is necessarily limited to these particular acid or ester derivatives. Nevertheless, it has been found that the most desirable acid and ester derivatives are those in which the carboxyl group has a relatively close proximity to the Z-mercapto sulfur atom.

It is also contemplated that the lubricating compositions of the invention can contain any of the conventional additives such as oxidation inhibiting pour depressants, corrosion inhibitors and the like.

What is claimed is: V v V 1. A lubricating oil composition comprising a major amount of a lubricating oil and a minor but load carrying Ordinarily about 2 to 40 wt,

C-S-(CHzhC 00R wherein n is an integer equal to 1 and 2, and R is an alkyl radical containing from 8 to 20 carbon atoms.

2. The lubricating oil composition of claim 1 wherein the amount of said compound is from 3 to 15% by weight, based on the weight of the total composition.

3. The lubricating oil composition of claim 1 wherein said compound is Z-mercaptobenzothiazole acetic acid C branched chain alkyl ester.

4.- The lubricating oil composition of claim 1 wherein R is an iso-octyl radical.

5. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and about 3 to 15 wt. percent, based on the weight of the total composition, of a compound having a structure corresponding to the following formula 10 wherein n is an integer equal to 1 and 2, and R is an alkyl radical containing from 8 to 20 carbon atoms.

6. A method for lubricating metal surfaces subjected to extreme pressure which comprises maintaining on said surfaces a lubricating oil containing a load carrying improving amount of a compound having the following wherein n is an integer equal to 1 and 2, and R is an alkyl radical containing from 8 to 20 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,725,382 Harmon Nov. 29, 1955 2,734,869 Mullen et a1 Feb. 14, 1956 2,796,404 Levin June 18, 1957 2,799,656 Mikeska et al. July 16, 1957 2,801,969 Morway et al. Aug. 6, 1957 2,841,556 Swenson et al July 1, 1958 2,844,536 Morway July 22, 1958 

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A LUBRICATING OIL AND A MINOR BUT LOAD CARRYING IMPROVED AMOUNT OF A COMPOUND HAVING A STRUCTURE CORRESPONDING TO THE FOLLOWING FORMULA 